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/********************************************************************
* *
* THIS FILE IS PART OF THE OggVorbis 'TREMOR' CODEC SOURCE CODE. *
* *
* USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS *
* GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
* IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING. *
* *
* THE OggVorbis 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2002 *
* BY THE Xiph.Org FOUNDATION http://www.xiph.org/ *
* *
********************************************************************
function: packing variable sized words into an octet stream
********************************************************************/
/* We're 'LSb' endian; if we write a word but read individual bits,
then we'll read the lsb first */
#include <string.h>
#include <stdlib.h>
#include "misc.h"
#include "ogg.h"
static unsigned long mask[]=
{0x00000000,0x00000001,0x00000003,0x00000007,0x0000000f,
0x0000001f,0x0000003f,0x0000007f,0x000000ff,0x000001ff,
0x000003ff,0x000007ff,0x00000fff,0x00001fff,0x00003fff,
0x00007fff,0x0000ffff,0x0001ffff,0x0003ffff,0x0007ffff,
0x000fffff,0x001fffff,0x003fffff,0x007fffff,0x00ffffff,
0x01ffffff,0x03ffffff,0x07ffffff,0x0fffffff,0x1fffffff,
0x3fffffff,0x7fffffff,0xffffffff };
/* mark read process as having run off the end */
static void _adv_halt(oggpack_buffer *b){
b->headptr=b->head->buffer->data+b->head->begin+b->head->length;
b->headend=-1;
b->headbit=0;
}
/* spans forward, skipping as many bytes as headend is negative; if
headend is zero, simply finds next byte. If we're up to the end
of the buffer, leaves headend at zero. If we've read past the end,
halt the decode process. */
static void _span(oggpack_buffer *b){
while(b->headend<1){
if(b->head->next){
b->count+=b->head->length;
b->head=b->head->next;
b->headptr=b->head->buffer->data+b->head->begin-b->headend;
b->headend+=b->head->length;
}else{
/* we've either met the end of decode, or gone past it. halt
only if we're past */
if(b->headend<0 || b->headbit)
/* read has fallen off the end */
_adv_halt(b);
break;
}
}
}
void oggpack_readinit(oggpack_buffer *b,ogg_reference *r){
memset(b,0,sizeof(*b));
b->tail=b->head=r;
b->count=0;
b->headptr=b->head->buffer->data+b->head->begin;
b->headend=b->head->length;
_span(b);
}
#define _lookspan() while(!end){\
head=head->next;\
if(!head) return -1;\
ptr=head->buffer->data + head->begin;\
end=head->length;\
}
/* Read in bits without advancing the bitptr; bits <= 32 */
long oggpack_look(oggpack_buffer *b,int bits){
unsigned long m=mask[bits];
unsigned long ret;
bits+=b->headbit;
if(bits >= b->headend<<3){
int end=b->headend;
unsigned char *ptr=b->headptr;
ogg_reference *head=b->head;
if(end<0)return -1;
if(bits){
_lookspan();
ret=*ptr++>>b->headbit;
if(bits>8){
--end;
_lookspan();
ret|=*ptr++<<(8-b->headbit);
if(bits>16){
--end;
_lookspan();
ret|=*ptr++<<(16-b->headbit);
if(bits>24){
--end;
_lookspan();
ret|=*ptr++<<(24-b->headbit);
if(bits>32 && b->headbit){
--end;
_lookspan();
ret|=*ptr<<(32-b->headbit);
}
}
}
}
}
}else{
/* make this a switch jump-table */
ret=b->headptr[0]>>b->headbit;
if(bits>8){
ret|=b->headptr[1]<<(8-b->headbit);
if(bits>16){
ret|=b->headptr[2]<<(16-b->headbit);
if(bits>24){
ret|=b->headptr[3]<<(24-b->headbit);
if(bits>32 && b->headbit)
ret|=b->headptr[4]<<(32-b->headbit);
}
}
}
}
ret&=m;
return ret;
}
/* limited to 32 at a time */
void oggpack_adv(oggpack_buffer *b,int bits){
bits+=b->headbit;
b->headbit=bits&7;
b->headptr+=bits/8;
if((b->headend-=bits/8)<1)_span(b);
}
int oggpack_eop(oggpack_buffer *b){
if(b->headend<0)return -1;
return 0;
}
/* bits <= 32 */
long oggpack_read(oggpack_buffer *b,int bits){
long ret=oggpack_look(b,bits);
oggpack_adv(b,bits);
return(ret);
}
long oggpack_bytes(oggpack_buffer *b){
return(b->count+b->headptr-b->head->buffer->data-b->head->begin+
(b->headbit+7)/8);
}
long oggpack_bits(oggpack_buffer *b){
return((b->count+b->headptr-b->head->buffer->data-b->head->begin)*8+
b->headbit);
}
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